Crystal structure of N′′-benzyl-N′′-[3-(benzyl­dimethyl­aza­nium­yl)prop­yl]-N,N,N′,N′-tetra­methyl­guanidinium bis­(tetra­phenyl­borate)

Ioannis Tiritiris; Willi Kantlehner

doi:10.1107/S2056989015024639

. 2015 Dec 31;71(Pt 12):o1086–o1087. doi: 10.1107/S2056989015024639

Crystal structure of N′′-benzyl-N′′-[3-(benzyldimethylazaniumyl)propyl]-N,N,N′,N′-tetramethylguanidinium bis(tetraphenylborate)

Ioannis Tiritiris ^a, Willi Kantlehner ^a,^*

PMCID: PMC4719992 PMID: 26870511

Abstract

In the crystal structure of the title salt, C₂₄H₃₈N₄ ²⁺·2C₂₄H₂₀B⁻, the C—N bond lengths in the central CN₃ unit of the guanidinium ion are 1.3364 (13), 1.3407 (13) and 1.3539 (13) Å, indicating partial double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and the positive charge is delocalized in the CN₃ plane. The bonds between the N atoms and the terminal methyl groups of the guanidinium moiety and the four C—N bonds to the central N atom of the (benzyldimethylazaniumyl)propyl group have single-bond character. In the crystal, C—H⋯π interactions between the guanidinium H atoms and the phenyl C atoms of the tetraphenylborate ions are present, leading to the formation of a two-dimensional supramolecular pattern parallel to the ac plane.

Keywords: crystal structure, guanidinium salt, tetraphenylborate, C—H⋯π interactions

Related literature

For the crystal structures of alkali metal tetraphenylborates, see: Behrens et al. (2012a ▸). For the synthesis of N′′-[3-(dimethylamino)propyl]-N,N,N′,N′-tetramethylguanidine, see: Tiritiris & Kantlehner (2012b ▸). For the crystal structure of N,N,N′,N′,N′′-pentamethyl-N′′-[3-(trimethylazaniumyl)propyl]guanidinium bis(tetraphenylborate), see: Tiritiris (2013a ▸). For the crystal structure of N-[3-(benzyldimethylazaniumyl)propyl]-N′,N′,N′′,N′′-tetramethylguanidinium bis(tetraphenylborate), see: Tiritiris (2013b ▸).

Experimental

Crystal data

C₂₄H₃₈N₄ ²⁺·2C₂₄H₂₀B⁻
M _r = 1021.00
Monoclinic,
a = 20.3677 (9) Å
b = 12.1101 (5) Å
c = 25.5580 (12) Å
β = 112.507 (2)°
V = 5823.9 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 100 K
0.38 × 0.25 × 0.12 mm

Data collection

Bruker Kappa APEXII DUO diffractometer
70711 measured reflections
17795 independent reflections
13809 reflections with I > 2σ(I)
R _int = 0.032

Refinement

R[F ² > 2σ(F ²)] = 0.043
wR(F ²) = 0.117
S = 1.03
17795 reflections
709 parameters
H-atom parameters constrained
Δρ_max = 0.38 e Å⁻³
Δρ_min = −0.31 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▸); cell refinement: SAINT (Bruker, 2008 ▸); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▸); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015 ▸); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ▸); software used to prepare material for publication: SHELXL2014.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S2056989015024639/rz5181sup1.cif

e-71-o1086-sup1.cif^{(2.1MB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015024639/rz5181Isup2.hkl

e-71-o1086-Isup2.hkl^{(973.9KB, hkl)}

Click here for additional data file.^{(7.5KB, cml)}

Supporting information file. DOI: 10.1107/S2056989015024639/rz5181Isup3.cml

Click here for additional data file.^{(1.3MB, tif)}

. DOI: 10.1107/S2056989015024639/rz5181fig1.tif

The structure of the title compound with displacement ellipsoids drawn at the 50% probability level. Hydrogen atoms are omitted for clarity.

Click here for additional data file.^{(1.3MB, tif)}

ac . DOI: 10.1107/S2056989015024639/rz5181fig2.tif

C—H⋯π interactions (brown dashed lines) between the hydrogen atoms of the guanidinium ion and the phenyl rings (centroids) of the tetraphenylborate ions in the crystal structure of the title compound (view perpendicular to the ac plane). Hydrogen atoms not involved in hydrogen bonding are omitted.

CCDC reference: 1443781

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

Cg1, Cg2 and Cg3 are the centroids of the C31–C36, C43–C48 and C61–C66 aromatic rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2B⋯Cg1ⁱ	0.98	2.76	3.441	127
C15—H15A⋯Cg1ⁱⁱ	0.99	2.94	3.538	120
C17—H17A⋯Cg2ⁱⁱ	0.98	2.76	3.716	166
C4—H4A⋯Cg3ⁱⁱⁱ	0.98	2.88	3.840	169
C20—H20⋯Cg3^iv	0.95	2.91	3.719	144

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) .

Acknowledgments

The authors thank Dr W. Frey (Institut für Organische Chemie, Universität Stuttgart) for measuring the diffraction data.

supplementary crystallographic information

S1. Comment

The synthesis of N''-[3-(dimethylamino)propyl]-N,N,N',N'-tetramethylguanidine is well known in the literature (Tiritiris & Kantlehner, 2012b). Electrophiles can attack at both, on the imine nitrogen of the guanidine function, as well as on the nitrogen atom of the (dimethylamino)propyl group. By alkylation with two equivalents of dimethyl sulfate, a permethylated waxy guanidinium methyl sulfate salt was obtained. After anion exchange with sodium tetraphenylborate, crystalline N,N,N',N',N''-pentamethyl-N''-[3-(trimethylazaniumyl)propyl]guanidinium bis(tetraphenylborate) emerged, which has been structurally characterized (Tiritiris, 2013a). By alkylation with benzyl bromide and subsequent anion exchange, the here presented title salt is the second one in our serie, whose crystal structure has been determined. Prominent bond parameters in the guanidinium ion are: C1–N1 = 1.3407 (13) Å, C1–N2 = 1.3364 (13) Å and C1–N3 = 1.3539 (13) Å, indicating partial double-bond character. The N–C1–N angles are: 121.16 (9)° (N1–C1–N2), 119.26 (9)° (N2–C1–N3) and 119.57 (9)° (N1–C1–N3), which indicates a nearly ideal trigonal-planar surrounding of the carbon centre by the nitrogen atoms. The positive charge is completely delocalized on the CN₃ plane (Fig. 1). The bonds between the N atoms and the terminal C-methyl groups of the guanidinium moiety all have values close to a typical single bond [1.4639 (13)–1.4673 (14) Å]. The C–N bond lengths in the terminal benzyldimethylammonium group are slightly elongated [1.4994 (13)–1.5293 (13) Å]. The bond lengths and angles in the tetraphenylborate ions are in good agreement with the data from the crystal structure analysis of the alkali metal tetraphenylborates (Behrens et al., 2012a). C–H···π interactions between the hydrogen atoms of –N(CH₃)₂, –CH₂ and benzyl groups of the guanidinium ion and the phenyl carbon atoms (centroids: Cg1 = C31–C36, Cg2 = C43–C48 and Cg3 = C61–C66) of the tetraphenylborate ions are present, ranging from 2.76 (2) to 2.94 (2) Å (Fig. 2; Table 1). This leads to the formation of a two- dimensional supramolecular pattern along the ac plane. Such type of C–H···π interactions have been also observed in N-[3-(benzyldimethylazaniumyl)propyl]- N',N',N'',N''-tetramethylguanidinium bis(tetraphenylborate) (Tiritiris, 2013b).

S2. Experimental

The title compound was obtained by reaction of N''-[3-(dimethylamino)propyl]-N,N,N',N'-tetramethylguanidine (Tiritiris & Kantlehner, 2012b) with two equivalents benzyl bromide in acetonitrile. After evaporation of the solvent the crude N''-benzyl-N''-[3-(benzyldimethylazaniumyl)propyl]-N,N,N',N'-tetramethylguanidinium dibromide (I) was washed with diethylether and dried in vacuo. 1.52 g (2.8 mmol) of (I) was dissolved in 20 ml acetonitrile and 1.92 g (5.6 mmol) of sodium tetraphenylborate in 20 ml acetonitrile was added. After stirring for one hour at room temperature, the precipitated sodium bromide was filtered off. The title compound crystallized from a saturated acetonitrile solution after several weeks at 273 K, forming colorless single crystals. Yield: 2.20 g (77%).